Polymeric yarn and method for manufacturing

ABSTRACT

The invention relates to a yarn comprising polymeric filaments and/or polymeric staple fibers containing a filler, wherein said filler is a plurality of fibrils having an average length of between 50 μm and 200 μm.

The present invention is in the field of polymeric yarns and in particular it relates to a yarn comprising a number of polymeric filaments and/or polymeric staple fibers containing a filler, wherein said filler is a plurality of fibrils. The invention further relates to a process for manufacturing such yarn and to various uses of the yarn.

Examples of such yarns are disclosed in WO 2008/046476 and WO 2010/089410, the yarns thereof containing filaments and/or staple fibers which contain a hard component. The hard component may be a plurality of hard fibrils having an average diameter of at most 25 microns. Such yarns have good resistance against cutting and are therefore suitable for various applications such as protective apparels, gloves, socks and the like. The yarns of WO 2008/046476 and WO 2010/089410 were manufactured with a spinning process wherein a solution of a polymer, e.g. ultrahigh molecular weight polyethylene (UHMWPE), was mixed with the hard component and then spinning the mixture into a plurality of filaments. The filaments were subsequently drawn and wound on bobbins. Staple fibers were obtained from the same filaments by cutting or stretch breaking thereof.

It was observed however that during the manufacturing process, a rather large amount of the hard component became disembodied from the filaments and/or staple fibers forming the yarn. The disembodied hard component formed unwanted deposits on the hardware utilized to manufacture the yarn and may even pose a health concern, e.g. causing mechanical skin irritations. Furthermore, deposits of the hard component were found on machinery used to further process the known yarns, such as drawing equipment and weaving, braiding or knitting equipment. It was observed that said deposits may wear the machinery down, e.g. shortening the life time or increasing the need of periodical maintenance and cleaning.

Furthermore, it was also observed that the known yarns may show a deterioration of their properties during utilization. Without being bound to any explanation, the inventors attributed this unwanted phenomena to a diminishment of the amount of hard component in the filaments and/or staple fibers during the utilization of said yarn.

An aim of the invention may therefore be to provide yarn comprising a filler in the form of a plurality of fibrils, which yarn can be manufactured with a process wherein the formation of deposits of the filler on the hardware used to run said process is minimized. A further aim of the invention may be to provide a yarn comprising a filler in the form of a plurality of fibrils, the yarn having optimized properties over the known yarns. Further in particular, an aim of the present invention may be to provide a yarn comprising a filler in the form of a plurality of fibrils, which yarn show a lesser deterioration of its properties during utilization.

The invention provides a yarn comprising polymeric filaments and/or polymeric staple fibers containing a filler, wherein said filler is a plurality of fibrils, said plurality having an average length of between 50 μm and 200 μm 200 μm. Preferably, said average length of said plurality of fibrils is at most 180 μm, more preferably at most 150 μm. Preferably, said average length of said plurality of fibrils is at least 75 μm, more preferably at least 100 μm.

Preferably, said plurality of fibrils also has a mass averaged fibril diameter of at most at most 20 μm, more preferably at most 15 μm, even more preferably at most 10 μm, most preferably at most 8 μm. Preferably, said mass averaged fibril diameter is at least 1 μm, more preferably at least 3 μm.

It was observed that the yarn of the invention, also referred to herein as the inventive yarn, may be manufactured with a cleaner process, i.e. a process wherein less fouling due to filler depositions may occur. It was further observed that the inventive yarn may show a good retention of its properties during utilization.

Within the context of the present invention, polymeric fibers are understood to mean polymeric elongated bodies of indefinite length and with length dimension much greater than their transversal dimensions, e.g. width and thickness. The term polymeric fiber may also include a polymeric monofilament, a polymeric ribbon, a polymeric strip or a polymeric tape and the like, and can have a regular or an irregular cross-section. The polymeric fibers may have continuous lengths, known in the art as polymeric filaments, or discontinuous lengths, known in the art as polymeric staple fibers. A yarn according to the present invention is an elongated body comprising a plurality of polymeric fibers.

Within the context of the present invention, fibrils are understood to mean elongated bodies of a definite length wherein said length is greater than their transversal dimensions, e.g. width and thickness. The term fibril may also include a monofilament, a ribbon, a strip or a tape and the like, and can have a regular or an irregular cross-section. Preferably, the fibrils used in the present invention have a regular cross-section, more preferably a round cross-section, most preferably a substantially circular cross-section.

Preferably, the fibrils used in accordance to the invention are hard fibrils, i.e. fibrils produced out of a hard material. Hard in the context of the invention means at least harder than the polymeric filaments or polymeric staple fibers themselves without the hard fibrils. Preferably the material that is used to produce the hard fibrils has a Moh's hardness of at least 2.5, more preferably at least 4, most preferably at least 6. Good examples of suitable hard fibrils include, carbon based fibrils, glass fibrils, mineral fibrils or metal fibrils. Most preferred fibrils are mineral fibrils.

The fibrils and in particular the hard fibrils, e.g. glass, mineral or metal fibrils, may be produced by rotation-spinning techniques, well known to the skilled person. It may also be possible to produce the fibrils and in particular the hard fibrils as fibrils having a continuous length that are subsequently milled into a plurality of fibrils having the desired average length. In an alternative the fibrils used in accordance with the invention may be produced by jet spinning, optionally subsequently milled.

The yarn according to the invention may contain polymeric filaments or polymeric staple fibers. In general all polymers that may be used for the production of polymeric filaments and/or polymeric staple fibers are suitable for the present invention too. It is possible to use polymers that are processed from a melt into polymeric filaments and/or polymeric staple fibers, e.g. nylon and thermoplastic polyester, but also those that may be processed from a solution. Examples of suitable polymers are those chosen from the group consisting of polyamides and polyaramides, e.g. poly(p-phenylene terephthalamide) (known as Kevlar®); poly(tetrafluoroethylene) (PTFE); poly{2,6-diimidazo-[4,5b-4′,5′e]pyridinylene-1,4(2,5-dihydroxy)phenylene} (known as M5); poly(p-phenylene-2,6-benzobisoxazole) (PBO) (known as Zylon®); poly(hexamethyleneadipamide) (known as nylon 6,6), poly(4-aminobutyric acid) (known as nylon 6); polyesters, e.g. poly(ethylene terephthalate), poly(butylene terephthalate), and poly(1,4 cyclohexylidene dimethylene terephthalate); polyvinyl alcohols; and also polyolefins e.g. homopolymers and copolymers of polyethylene and/or polypropylene.

It is preferred that the polymer used in the present invention is a polyolefin, more preferably a polypropylene or a polyethylene, most preferably an ultrahigh molecular weight polyethylene (UHMwPE). By UHMwPE is herein understood a polyethylene having an intrinsic viscosity (IV) as measured on solution in decalin at 135° C., of at least 5 dl/g. Preferably, the IV of the UHMWPE is at least 10 dl/g, more preferably at least 15 dl/g, most preferably at least 21 dl/g. Preferably, the IV is at most 40 dl/g, more preferably at most 30 dl/g, even more preferably at most 25 dl/g.

The yarn according to the invention may contain polymeric filaments or polymeric staple fibers comprising between 0.1 wt % and 55 wt % of filler, wherein the wt % of the filler is calculated based on the total weight of the polymeric filaments and/or polymeric staple fibers as the case may be. Preferably said wt % of the filler is between 1 and 30, more preferably between 2 wt % and 20 wt %, most preferably between 3 wt % and 10 wt %.

The titer of the polymeric filaments and/or polymeric staple fibers of the inventive yarn is preferably at most 15 dtex, more preferably at most 10 dtex, most preferably at most 5 dtex. Preferably, said titer is at least 1 dtex, more preferably at least 1.5 dtex, most preferably at least 2 dtex. It was observed that good results, in particular when UHMWPE was used to produce the filaments and/or the staple fibers, were obtained when said titer was chosen in the afore-mentioned ranges.

The inventive yarn can be produced with methods known in the art, e.g. the methods disclosed in WO 2008/046476 or WO 2010/089410, both incorporated herein by reference. Therein, the yarn was produced by (i) providing a composition comprising the polymer and the filler; (ii) melting or dissolving the polymer while mixing said polymer and said filler; (iii) spinning filaments from the melt or the solution of step (ii); and optionally cutting and/or stretch breaking the filaments obtained at step (iii) into staple fibers.

If UHMwPE is used as the polymer in accordance with the invention, the inventive yarn is preferably produced by a gel spinning process. The gel-spinning process is for example described in EP 0205960 A, EP 0213208 A1, U.S. Pat. No. 4,413,110, GB 2042414 A, EP 0200547 B1, EP 0472114 B1, WO 01/73173 A1, and Advanced Fiber Spinning Technology, Ed. T. Nakajima, Woodhead Publ. Ltd (1994), ISBN 1-855-73182-7, and references cited therein. Gel spinning is understood to include at least the steps of spinning at least one filament from a solution of the polymer, e.g. UHMwPE, and the filler in a suitable solvent for the polymer; cooling the filament obtained to form a gel filament; removing at least partly the spin solvent from the gel filament; and drawing the filament in at least one drawing step before, during or after removing spin solvent. To obtain gel-spun staple fibers, the gel-spun filaments may be cut or stretch broken.

In a preferred embodiment of the invention, the inventive yarn is a so-called composite yarn. A composite yarn is a yarn that contains one or more inventive yarns and one or more further yarns, i.e. yarns different from the inventive yarn, e.g. yarns manufactured from a different polymer and/or containing a different filler but also a glass, a metal or a ceramic yarn, wire or thread. The further yarns may cover the inventive yarn as a sheath or they may be used as a core while the inventive yarn covers said core as a sheath.

The inventive yarns can be used in a plethora of applications e.g. fabrics, architectural textiles, ropes, fishing lines and fishing nets, and cargo nets, straps, and restraints in shipping and aviation, gloves and other protective apparel. Thus in one respect the invention relates to an article, preferably a rope, a protective apparel, a fishing line, a net, or a medical device comprising the yarns of the invention.

In particular the invention relates to a fabric containing the yarn according to the invention. The fabric of the invention may be made by knitting, weaving or by other methods, by using conventional equipment. It is also possible to produce non-woven fabrics. The invention also relates to products containing the fabric of the invention.

In a further aspect, the invention relates to garments intended to protect persons from being cut or stabbed, e.g. the persons working in the meat industry, the metal industry or the wood industry, said garments containing the inventive yarn or the fabric of the invention. Examples of such garments include gloves, aprons, trousers, cuffs, sleeves, and the like.

In yet a further aspect, the invention relates to side curtains and tarpaulins for trucks, soft sided luggage, commercial upholstery, airline cargo container curtains, fire hose sheathes containing the inventive yarns or the fabric of the invention.

Surprisingly the inventive yarns are also suitable for use in protective products against injury by stabbing with, for example, a knife or an ice pick. An example of such a product is a vest for life protection used by police officers. Preferably in such a product used for protection, the inventive yarns are located at the side of the product which will be hit by the stabbing object.

Surprisingly the inventive yarns are also suitable for use in protective garments against injury by slashing with a sharp object, e.g. knives.

FIGURE shows the different wear levels on machinery induced by the inventive yarn (a) and by a known yarn (b).

The invention will be further explained in detail with the help of the following examples and comparative experiments without being however limited thereto.

Methods for Measurement

-   -   The average length of a plurality of fibrils may be calculated         by measuring the length of at least 500 fibrils and averaging         the results. The length of a fibril can be determined by optical         or electronic microscopy. Any commercial image recognition         software can be employed to speed up the determination of the         length of a large number of fibrils.     -   The mass average fibril diameter can be calculated by measuring         the diameter of all fibrils contained by a mass of fibrils of at         least 0.5 grams and averaging the results. By diameter is herein         understood the longest distance between two opposite points on         the circumference of a cross-section of the fibril. The diameter         of a fibril can be determined by optical or electronic         microscopy. Any commercial image recognition software can be         employed to speed up the determination of the diameter of a         large number of fibrils.     -   IV: the Intrinsic Viscosity is determined according to method         ASTM D1601(2004) at 135° C. in decalin, the dissolution time         being 16 hours, with BHT (Butylated Hydroxy Toluene) as         anti-oxidant in an amount of 2 g/l solution, by extrapolating         the viscosity as measured at different concentrations to zero         concentration;

Comparative Experiment A

A dry blend was produced in a tumbler, the dry blend consisting of 5 wt. % of mineral fibrils, sold under the trade name RB220ELS by Lapinus, NL, and 95 wt. % of a UHMwPE with an IV of 27.0 dl/g. RB220ELS fibrils have an average length of about 230 μm and a mass averaged fibril diameter of about 9.0 μm. The blend was then mixed with decalin, a solvent for the UHMwPE in a concentration of 9 wt. %. The so obtained solution was fed to a twin screw extruder having a screw diameter of 25 mm, equipped with a gear pump. The solution was heated in this way to a temperature of 180° C. The solution was pumped through a spinneret having 64 holes, each hole having a diameter of 1 millimeter. The so obtained filaments were drawn in total with a factor of at least 80 and dried in a hot air oven. After drying the filaments were bundled into a yarn and wound on a bobbin. Depending on the stretch factors, filaments having different titers were obtained.

The amount of fibrils that became disembodied from the filaments during the yarn manufacturing process was measured.

The yarn was knitted into a fabric of 260 grams per square meter.

The wear of the knitting machine during processing of the yarn was investigated. The results are given in Table 1.

EXAMPLE 1

Comparative Experiment was repeated with the difference that a mineral fibril known as CoatForce® CF10ELS also from Lapinus was used instead of the RB220ELS fibrils. CoatForce® CF10ELS consists of a plurality of hard fibrils having an average length of about 125 μm and a mass averaged fibril diameter of about 7.0 μm. All results are given in Table 1.

TABLE 1 Deposits per about Relative loss Sample 100 Kg of yarn (g) (%) Comp. Exp. A 66.7 1.3 Example 1 38.9 0.7

Comparative Experiment B

Comparative Experiment A was repeated with an amount of 7 wt % fibrils instead of 5 wt %. Results are presented in Table 2.

Experiment 2

Comparative Experiment B was repeated with CF10ELS instead of RB220ELS. Results are presented in Table 2.

TABLE 2 Gain in amount of filler retained in the yarns of Example Dtex per filament (%) 4.6 8 3.8 8 3.3 6 2.9 4

The gain in the amount of filler retained in the yarns of the Example was computed with Formula 1:

$\begin{matrix} {{{gain}\mspace{14mu} (\%)} = {\frac{M_{Ex} - M_{CEx}}{M_{Ex}} \times 100}} & {{Formula}\mspace{14mu} 1} \end{matrix}$

wherein M_(Ex) is the percentage of the filler in the filaments and/or staple fibers contained by the yarn of the Example; and M_(CEx) is the respective percentage of the filler calculated for the yarn of the Comparative Experiment.

The fabrics obtained were also tested against abrasion resistance according to EN 388 “Martindale Abrasion Testing”. It was observed that for the fabrics using the yarns of the invention, an increase with about 50% in abrasion resistance was achieved.

FIGURES (a) and (b) show that the wear (100) induced on the machinery by the yarns of the invention is much reduced in comparison with the wear (101) induced under similar conditions by a yarn such as the one of the Comparative Experiment A. 

1. A yarn comprising polymeric filaments and/or polymeric staple fibers containing a filler, wherein said filler is a plurality of fibrils having an average length of between 50 μm and 200 μm.
 2. The yarn of claim 1 wherein the average length of said plurality of fibrils is at most 180 μm, more preferably at most 150 μm.
 3. The yarn of claim 1 wherein said average length of said plurality of fibrils is at least 75 μm, preferably at least 100 μm.
 4. The yarn of claim 1 wherein the plurality of fibrils has a mass averaged fibril diameter of at most at most 20 μm, more preferably at most 15 μm, even more preferably at most 10 μm, most preferably at most 8 μm.
 5. The yarn of claim 1 wherein the plurality of fibrils has a mass averaged fibril diameter is at least 1 μm, more preferably at least 3 μm.
 6. The yarn of claim 1 wherein the fibrils are hard fibrils.
 7. The yarn of claim 1 wherein the fibrils are hard fibrils having a Moh's hardness of at least 2.5.
 8. The yarn of claim 1 wherein the polymer used to manufacture the polymeric filaments and/or staple fibers is a polyolefin, more preferably a polypropylene or a polyethylene.
 9. The yarn of claim 1 wherein the polymer used to manufacture the polymeric filaments and/or staple fibers is an ultrahigh molecular weight polyethylene (UHMwPE).
 10. The yarn of claim 1 wherein the polymeric filaments and/or polymeric staple fibers comprise between 0.1 wt % and 55 wt % of filler.
 11. A composite yarn containing one or more of any one of the yarns of claim 1 and one or more further yarns, wherein the further yarns are preferably yarns manufactured from a glass, a metal or a ceramic material.
 12. Fabrics, architectural textiles, ropes, fishing lines and fishing nets, cargo nets, straps and restraints for shipping and aviation comprising the yarn of claim
 1. 13. Garments, in particular gloves, aprons, trousers, cuffs and sleeves comprising the yarn of claim
 1. 14. Protective products against injury by stabbing comprising the yarn of claim
 1. 15. Protective garments against injury by slashing comprising the yarn of claim
 1. 